Various devices for transmitting motions, both in the axial direction and in the direction of rotation, between an outer tube and an inner tube are previously known. The majority are realized as a thread between the tubes, either the outer tube or the inner tube being used to achieve the rotation. These devices are often used in table legs, white goods and other applications in which there is a need to make a height adjustment and effect levelling against the floor. This works well when dealing with small tube dimensions. Where larger dimensions are involved, it creates problems. A type of “drawer effect” is then obtained, which increases the greater the dimensions of the tubes. There are an endless number of devices for converting a rotary motion into a linear motion. Likewise, there are an endless number of devices for converting a linear motion into a rotary motion. These are not made to achieve simultaneous linear and rotary transmission. Air dampers comprising a twist sleeve of flexible material, the cross section of which substantially conforms to the duct in which the flow takes place, are previously known. One end of the twist sleeve is fixed in relation to the duct and the other end can be rotated, whereupon the free area in the centre decreases in relation to the original state.
There are some known solutions for rotating the twist sleeve, but when it is a matter of, from the outer side of an outer tube, achieving an axial and, at the same time, rotary motion of the twist sleeve, there is currently no solution for this. The motion should also be able to be indicated for fine adjustment. Likewise, no flow in the outer tube must leak out. It is especially difficult to achieve this when larger tube diameters are involved.
In addition, there are some known solutions for rotating the twist sleeve from the outer side of the outer tube with cords. There are also known solutions for rotating damper valves with cords from the inner side of an outer tube. But where it is a matter of achieving in an outer tube an axial and, at the same time, rotary motion of the twist sleeve with cords from the outside, there is currently no solution for this.